The present invention relates to the field of tribology and, more particularly, to a method and apparatus for testing and measuring friction, wear characteristics of materials, and tribological properties of lubricants.
Tribology is a science of friction, wear, and lubrication on friction surfaces. Many different types of friction testers, tribometers, and other devices for measuring various parameters of friction are known. U.S. Pat. No. 5,795,990 issued in 1998 to N. Gitis, et al. describes a friction tester which has a horizontal base with a vertical column that supports vertical guides for guiding a carriage. FIG. 1 is a fragmental sectional view of the aforementioned tester, which has a lower base 10, and a vertical column (not shown). A carriage 16 supports a rotary stepper motor (not shown) that rotates an upper specimen holder 64 via a reducer 66. The upper specimen holder 64 is strictly coaxial with the center of a bowl 22, which is supported by the lower base 10 via a lower plate 24. The upper specimen holder 64 has a radial guiding slot, which serves for guiding a slider 68, the position of which can be adjusted by means of a micrometric screw. The upper specimen holder 64 supports a collet chuck 19 that holds an upper specimen 20 by means of a coupling 76 supported in the upper specimen holder 64 by means of an angular adapter 78 which has a horizontal axle 80 inserted into an opening of the slider 68.
A sensor, e.g., a load cell 29, is placed between the lower plate 24 and an intermediate plate 30 for measuring a friction force and friction torque developed during testing between the upper specimen 20 and a lower specimen 21.
Thus, in the known tester of U.S. Pat. No. 5,795,990, the slider and the collet chuck 19 together with the upper specimen 20 perform orbital movements over the stationary lower specimen 21. Rotation of these relatively heavy parts develops centrifugal forces which deform, i.e., bends, the rotating chuck 19 with the upper specimen 20 radially outwardly from the vertical axis of rotation. It is impossible to obtain accurate measurements and it is difficult to provide electrical connections with the rotating parts, e.g., if a heater is installed on a rotating part. Furthermore, the orbital rotation of aforementioned heavy parts limits frequency of rotation (which did not exceed 60 rpm in a real tester) and requires the use of the reducer 66 (which was a harmonic drive reducer in a real tester).
Another disadvantage of the known tester is lack of versatility resulting from the upper attachment of the rotating parts. Such an arrangement limits a space for attachment of various replaceable modules, such as modules with heating, reciprocating drives, etc.
In the known tester the sensor 29 is located beneath the bowl 22 and all other fixtures, so that the weight of these devices acts on the sensor and therefore does not allow obtaining accurate measurements.
It is an object of the present invention to provide an apparatus for testing and measuring tribological properties of the materials and lubricants which is simple in construction, reliable in operation, universal in use, allows testing with high frequencies of rotation and under different temperatures, prevents deformations in the friction force measurement system, and therefore ensures accurate measurements. Another object of the invention is to provide a method for testing and measuring tribological properties of the materials and lubricant which is reliable and allows testing in a wide range of operation conditions.